Blindfire Marksman Trophy in Uncharted 3: Drake's Deception

This trophy is relatively easy and can be earned quite early on. To blind fire in cover you must first be in cover by pressing against an obstacle and then firing by pressing (i.e. without the aid of holding down to aim). You must manipulate the screen with to try and position the enemy centrally to the screen before firing for best results.

This action is best done with a high powered weapon with spray rounds like the Sawn-Off or the Pistole at close range. An excellent place to farm this is in Chapter 6 - The Château right after you ascend the well and appear in the front grounds. The first enemy is stealth killed by pulling him into the well, but jump up and take cover behind the outer rim of the well and begin firing. At least a few of the enemies will creep out of cover and try to flank/melee you, this is a perfect time to land a free cover kill. When nobody else will move, save/load and repeat until you have the required amount of kills. One carries a Sawn Off so watch out for him and pick it up after you kill him.

Alternatively, grab a SAS - 12 from the first batch of guards in Chapter 16 - One Shot at This and keep it until the part where you drop through the skylight. Once the jeep turns up (which can be blown up for Dyno-Might Master) take cover against the nearest pillar and squeeze a shot off. Enemies will come steaming in attempting to flank you so kill them with the shotgun until all the ammo is gone, before doing the Save/Load technique.